Towel bar hub



FIG. 1 is a front perspective view of a towel bar hub showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken line showing of various regions represents unclaimed subject matter and forms no part of the claimed design. 

CLAIM The ornamental design for a towel bar hub, as shown and described. 